Identifiers are in beta. An identifier, once assigned, is permanent and will not change. The class model, the name forms and the coverage are under review with CEOS colleagues and may change before the first stable edition. Coverage is also still being completed: records added since the current edition was minted have no identifier yet, a small number of duplicate records are being reconciled before their surviving record is assigned one, and identifiers for measurements and measurement variables are not yet shown on their own pages. Coverage grows by loading new editions; the edition currently loaded is shown above.

Every mission, instrument, agency, constellation, series, programme, measurement, measurement variable and horizon record in the CEOS Database carries a canonical identifier: a short, lower-case, URL-safe name such as sentinel-1-a, c-band-sar or isa. It is the stable handle for that record. Names in the database change as agencies rename programmes, correct spellings or consolidate records. The identifier does not.

The record types in the CEOS Database line up with the classes proposed for harmonised EO identifiers - programme, constellation, mission, platform, instrument, sensor - although the two vocabularies use some of the same words for different things. This is the mapping, and whether each identifier is minted - assigned once and held in the registry - or derived - built from identifiers that were.

Each record carries a full name, a short name and the identifier. The identifier is the proposal's "mnemonic"; the eight-character cap that term usually carries was relaxed here for readability, so a mission is sentinel-1-a rather than something compressed to fit. A separate acronym exists only where the database holds one - it is a curated field, populated on a handful of records - so the Acronym column on the identifier table is left blank rather than repeating the short name.

An identifier is minted once, when a record first enters the registry, and is never reassigned to a different record. If a record is later merged or retired, its identifier is retired with it and points to the surviving record, which keeps its own identifier. A duplicate record never receives an identifier of its own, so the plain name stays reserved for the record that survives.

One instrument on one platform is named by combining the two identifiers rather than by minting a third: <mission-slug>_<instrument-slug>, for example sentinel-1-a_c-band-sar. Dashes appear only inside an atom and the underscore is only ever the joiner, so a combination always parses back into the two identifiers it was built from. The same pair has a hierarchical form as well, missions/<mission-slug>/instruments/<instrument-slug>, which is how it is addressed in the API. Combinations are derived, not minted: they appear on the mission and instrument pages, and they are not rows in the registry.

The identifier is derived from the record's short name. Where two genuinely distinct records would produce the same name, the later one is qualified with a distinguishing term such as its mission, series or agency, and the plain form stays with the incumbent. Once assigned, the form never changes, even if the rule that produced it does.

Measurements and measurement variables carry identifiers too, on the same terms as any other: minted once, permanent, never reissued. They sit outside the class model above. A measurement is the CEOS Database category - ocean colour, for example - and a measurement variable is the WMO/GCOS quantity beneath it. They are vocabularies this database maintains rather than classes in the platform-to-sensor ontology, and they are listed here because their identifiers are permanent, not because they are part of it.

The registry is maintained alongside the CEOS EO-GOS API (eogos-api) and loaded into this database in editions. Each edition is identified by a content hash. The edition this site is reading is shown at the top of this page, and every identifier on a record page names its edition and mint date. Re-loading an edition changes nothing. A new edition only adds identifiers, for records created since the last edition or for records whose duplicates have been reconciled.

A small number of records have no identifier yet: records added since the current edition was minted, duplicate records awaiting reconciliation, and in-situ instruments not linked to any mission. These are tracked for curation and receive identifiers in the next edition. Their pages simply omit the Identifier row.

Cite a record by its canonical identifier together with the database name, for example "CEOS Database mission sentinel-1-a". The same identifiers are used across CEOS data services built on this database, so a citation made today will still resolve to the same record in future editions.